While, as liquid crystal projectors (projectors wherein a liquid crystal panel is used as a light valve), those which use a transmissive liquid crystal panel and those which use a reflective liquid crystal panel are available, it is considered that conventionally liquid crystal projectors of both types are usually installed and used in a house and the like. As disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. Sho 63-118125) or Patent Document 2 (Japanese Patent Application Laid-Open No. Hei 4-60538), a lamp such as a metal halide lamp, a high-pressure mercury lamp or a xenon lamp is used as the light source.
However, where a lamp is used as the light source, there are such problems as (a) the aperture of the light source section becomes large and the overall size of the projector becomes large, (b) a cooling apparatus such as a fan is required and the overall size of the projector becomes larger, (c) noise by the fan and so forth is loud and also the power consumption is high, (d) light in an unnecessary and harmful wavelength region such as ultraviolet rays is irradiated, resulting in the possibility that the reliability of the liquid crystal panel for which an organic substance is used may be spoiled, (e) the light source cannot be turned on and off at a high speed and also the adjustment of the light amount is difficult, (f) exchange of the lamp is required frequently due to disconnection or the life of the lamp, and so forth.
Therefore, an idea is considered to use a light emitting device (luminous element) other than a lamp as the light source of a liquid crystal projector.
In particular, Patent Document 3 (Japanese Patent Application Laid-Open No. 2005-116799) and Non-Patent Document 1 (G. Harbers, M. Keuper, S. Paolini; “Performance of High Power LED Illuminators in Color Sequential Projection Displays”, IDW '03 p. 1585 to p. 1588) discloses that an LED (light emitting diode) is used as the light source.
Further, Patent Document 4 (JP-T-2005-526288) discloses that a laser is used as the light source such that pumping thereof is controlled for each pixel in a raster pattern and a laser beam emitted from the laser is scanned on the raster pattern by means of a scanner composed of two scanning mirrors to display a two-dimensional image on the raster pattern.
As for the laser, solid-state lasers such as a semiconductor laser, a so-called LD and a solid-state laser (DPSSL: Diode Pumped Solid State Laser) which is pumped by a semiconductor laser have been implemented, and as regards the size, the semiconductor laser can be formed such that the length of one side thereof is approximately several hundreds μm, and with nonlinear optical crystal of the solid-state laser, the size can be made approximately several mm at the 100 mW output class.
Further, the semiconductor laser or the solid-state laser has a long life in comparison with the metal halide lamp and so forth and hardly requires replacement, and is high in light emission efficiency, low in heat generation and easy to cool.
Further, the semiconductor laser or the solid-state laser can be configured so as to emit light of wavelengths optimum for display within wavelength regions of red, green and blue depending upon the type and the composition of crystal, thereby the color purity is enhanced and light unnecessary for display such as infrared rays and ultraviolet rays is not emitted.
Furthermore, the semiconductor laser or the solid-state laser can carry out on/off switching in a moment thereby able to readily control the amount of light to be emitted.